Imagine scattering puzzle pieces on a table top, then vibrating the table until the pieces all fit into place, solving the puzzle. That’s a crude description of self-assembly, but some molecules like to combine with others when they get into the right position. Using sound waves opens up new possibilities, like assembly in three dimensions while suspended in solution. Perhaps different sound patterns could produce different assembly patterns.

An elegantly simple experiment with floating particles self-assembling in response to sound waves has provided a new framework for studying how seemingly lifelike behaviors emerge in response to external forces.

Close up photograph of the self-assembling particles in the clear acrylic tube. These particles consist of cut plastic straws (blue) sealed to a flat plastic chip (black), which float on top of a water-glycerin solution. (Credit: Chad Ropp/Berkeley Lab)
Scientists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) demonstrated how particles, floating on top of a glycerin-water solution, synchronize in response to acoustic waves blasted from a computer speaker.